It is generally known to provide a vehicle including an active front steering system and including a solenoid for locking the front steering system. It is also generally known to provide a vehicle including a locking solenoid of an active front steering system that makes an objectionable “click” noise every time the vehicle is shut down. The active front steering (AFS) system may add and subtract angle between the driver steering wheel input and the steering gear input shaft. The active front steering system consists of an electronic control unit (ECU), a motor, a gear and a locking device all integrated into the steering wheel. The locking unit may provide a mechanical connection between the steering wheel and wheels during power-off of the AFS system (i.e., before and/or after shutting down the engine) and it may provide a means to lock the actuator in case of a severe failure in the AFS system. The locking unit may include a solenoid attached to the steering wheel armature, a pin having a spring for biasing the pin in a direction toward a locked position and a locking disc connected to the motor shaft, the disc including pockets or spaces for receiving the end of the pin and for locking the AFS system.
The active front steering (AFS) system can add and subtract angle between the driver steering wheel input and the steering gear input shaft. In one known embodiment, the AFS system consists of an electronic control unit (ECU), a motor, a gear and a locking device all integrated into the steering wheel. The locking unit may provide a mechanical connection between the steering wheel and the wheels of the vehicle during power-off of the system (i.e., after shutting down of the engine). The locking unit may also provide a lock of the AFS system in case of a severe failure in the AFS system or some other input.
While it is known to use a solenoid and locking pin as a lock actuator for an AFS system, it generates objectionable noise when contacting the locking disc. When the current is removed from the solenoid coil, the solenoid pin begins to accelerate from the force of the coil spring of the solenoid which biases the locking pin toward the locked position. When the moving solenoid pin makes contact with the lock plate, an objectionable “click” noise or sound is produced. In one known application, the locking solenoid of the active front steering system makes a noise every time the vehicle is shut down. Despite this long known problem with such systems, there remains a very significant need for an effective solution to eliminate the noise of such systems and yet be operable in the unique operating environment of the AFS system.